But do those other cables generate audio frequency fields of comparable
strength?

The details of the amplification and equalisation are way beyond me (who
avoided electronics like a plague dog) but it seems to make sense given
the field strengths mandated according to Wikipedia: "an induction loop
system ... must be capable of delivering field strength peaks of 400mA/m
+- 3 dB"

PS

I mean no criticism when I say I was reminded of the economist's
question: "It's all very well to know it works in practice, but does it
work in theory?"

On 24/02/2018 11:44, Brian Gaff wrote:
Yes quite how one turn of wire can generate enough field to interact with
the coil in a hearing aid is a bit of a black art. One might imagine the
other cables like mains and network and powerline internet connections would
generate such an intense field it would never work.